As known to those skilled in the art, degradation of rubber from ozone manifests itself by (a) cracks appearing perpendicular to the stress in the rubber and (b) the appearance of a silvery film or frosting on the surface of the article. The attack of ozone is purely a surface phenomenon. The function of the antiozonant depends on its migration to the surface of the rubber article where the battle against the ozone attack can occur.
Conventional diphenyldiamine antiozonants, such as N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamines, are widely used in the protection of rubber. Whereas use of these diphenyldiamine antiozonants have in the past proved quite satisfactory, recent developments in rubber technology have resulted in rubber products with extended service lives and, therefore, require commensurate protection from ozonolysis. These recent developments are particularly apparent in tires. Use of diphenyldiamine antiozonants in compounded diene rubbers have not affected the continued need for cure accelerators in such rubbers and as one can appreciate, the more additives required, generally the more expensive and variables one has to consider in producing the rubber article. Therefore, there exists a need for a compound offering extended protection from ozonolysis of rubber while concomitantly functioning as a cure accelerator.